A dormant wireless transmit receive unit (WTRU) is a WTRU that has a radio resource control (RRC) connection to the eNodeB, has established radio bearers, is known on cell level, but has activated discontinuous reception (DRX) for power saving during temporary inactivity. A WTRU can be quickly moved to this dormant “sub-state”, and the latency for transition from dormant to active affects the quality of service (QoS). For a transition to active state, a dormant WTRU with uplink synchronization may request uplink data transmission via transmitting a Scheduling Request (SR) on the physical uplink control channel (PUCCH), in order to receive an access grant to the physical uplink shared channel (PUSCH). The following is an example of latency components for the transition to the active state based on current long term evolution (LTE) specifications for an error-free SR. Assuming a periodic PUCCH configured for SR is scheduled every 5 ms, the average waiting time is 2.5 ms. The transmission of an SR can be repeated until a scheduling grant is received. Assuming the first SR is successfully received by the eNodeB, the scheduling grant can be sent by the eNodeB after a 3 ms processing delay. If the grant is received in sub-frame n, the uplink (UL) data can be transmitted in sub-frame n+4, giving 3 ms for WTRU processing. With an uplink data transmission duration of 1 ms, the total transition delay can be 11.5 ms. The 3GPP LTE Advanced system aims for latency of the dormant to active transition of 10 ms, excluding the DRX cycle. The 10 ms transition includes initial message transmission, with a message size that fits one transmission time interval (TTI). Only error free transmission of data and signaling is assumed to fulfill the LTE-A target performance.
A contention-based (CB) uplink data transmission is sent only in uplink resource blocks (RBs) that have not been used for contention-free (CF) uplink transmission. A CB transmission allows uplink synchronized WTRUs to transmit uplink data without sending a scheduling request (SR) in advance, which reduces the latency and the signaling overhead. CB grants are received by the WTRU in a downlink and are used to assign unused resources on a per sub-frame basis. Thus, for small data packets, the packet may be more efficiently transmitted on a CB channel compared to a scheduled one. The CB transmission can also include a buffer status report (BSR), which provides the serving eNodeB with information about the amount of data available for transmission in the uplink buffers of the WTRU. A “regular BSR” is triggered when uplink data for a logical channel becomes available for transmission and either the data belongs to a logical channel with higher priority than the priorities of other logical channels and for which data is already available for transmission, or there is no data available for transmission for any of the logical channels. There are also other types of BSRs that are triggered by other trigger conditions.